Deconstruction of Corticospinal Circuits for Goal-Directed Motor Skills.

Corticospinal neurons (CSNs) represent the direct cortical outputs to the spinal cord and play important roles in motor control across different species. However, their organizational principle remains unclear. By using a retrograde labeling system, we defined the requirement of CSNs in the execution of a skilled forelimb food-pellet retrieval task in mice. In vivo imaging of CSN activity during performance revealed the sequential activation of topographically ordered functional ensembles with moderate local mixing. Region-specific manipulations indicate that CSNs from caudal or rostral forelimb area control reaching or grasping, respectively, and both are required in the transitional pronation step. These region-specific CSNs terminate in different spinal levels and locations, therefore preferentially connecting with the premotor neurons of muscles engaged in different steps of the task. Together, our findings suggest that spatially defined groups of CSNs encode different movement modules, providing a logic for parallel-ordered corticospinal circuits to orchestrate multistep motor skills.

Benzodiazepine administration patterns before escalation to second-line medications in pediatric refractory convulsive status epilepticus.

OBJECTIVE: This study was undertaken to evaluate benzodiazepine (BZD) administration patterns before transitioning to non-BZD antiseizure medication (ASM) in pediatric patients with refractory convulsive status epilepticus (rSE). METHODS: This retrospective multicenter study in the United States and Canada used prospectively collected observational data from children admitted with rSE between 2011 and 2020. Outcome variables were the number of BZDs given before the first non-BZD ASM, and the number of BZDs administered after 30 and 45 min from seizure onset and before escalating to non-BZD ASM. RESULTS: We included 293 patients with a median (interquartile range) age of 3.8 (1.3-9.3) years. Thirty-six percent received more than two BZDs before escalating, and the later the treatment initiation was after seizure onset, the less likely patients were to receive multiple BZD doses before transitioning (incidence rate ratio [IRR] = .998, 95% confidence interval [CI] = .997-.999 per minute, p = .01). Patients received BZDs beyond 30 and 45 min in 57.3% and 44.0% of cases, respectively. Patients with out-of-hospital seizure onset were more likely to receive more doses of BZDs beyond 30 min (IRR = 2.43, 95% CI = 1.73-3.46, p < .0001) and beyond 45 min (IRR = 3.75, 95% CI = 2.40-6.03, p < .0001) compared to patients with in-hospital seizure onset. Intermittent SE was a risk factor for more BZDs administered beyond 45 min compared to continuous SE (IRR = 1.44, 95% CI = 1.01-2.06, p = .04). Forty-seven percent of patients (n = 94) with out-of-hospital onset did not receive treatment before hospital arrival. Among patients with out-of-hospital onset who received at least two BZDs before hospital arrival (n = 54), 48.1% received additional BZDs at hospital arrival. SIGNIFICANCE: Failure to escalate from BZDs to non-BZD ASMs occurs mainly in out-of-hospital rSE onset. Delays in the implementation of medical guidelines may be reduced by initiating treatment before hospital arrival and facilitating a transition to non-BZD ASMs after two BZD doses during handoffs between prehospital and in-hospital settings.

Factors associated with long-term outcomes in pediatric refractory status epilepticus.

OBJECTIVE: This study was undertaken to describe long-term clinical and developmental outcomes in pediatric refractory status epilepticus (RSE) and identify factors associated with new neurological deficits after RSE. METHODS: We performed retrospective analyses of prospectively collected observational data from June 2011 to March 2020 on pediatric patients with RSE. We analyzed clinical outcomes from at least 30 days after RSE and, in a subanalysis, we assessed developmental outcomes and evaluated risk factors in previously normally developed patients. RESULTS: Follow-up data on outcomes were available in 276 patients (56.5% males). The median (interquartile range [IQR]) follow-up duration was 1.6 (.9-2.7) years. The in-hospital mortality rate was 4% (16/403 patients), and 15 (5.4%) patients had died after hospital discharge. One hundred sixty-six (62.9%) patients had subsequent unprovoked seizures, and 44 (16.9%) patients had a repeated RSE episode. Among 116 patients with normal development before RSE, 42 of 107 (39.3%) patients with available data had new neurological deficits (cognitive, behavioral, or motor). Patients with new deficits had longer median (IQR) electroclinical RSE duration than patients without new deficits (10.3 [2.1-134.5] h vs. 4 [1.6-16] h, p = .011, adjusted odds ratio = 1.003, 95% confidence interval = 1.0008-1.0069, p = .027). The proportion of patients with an unfavorable functional outcome (Glasgow Outcome Scale-Extended score ≥ 4) was 22 of 90 (24.4%), and they were more likely to have received a continuous infusion. SIGNIFICANCE: About one third of patients without prior epilepsy developed recurrent unprovoked seizures after the RSE episode. In previously normally developing patients, 39% presented with new deficits during follow-up, with longer electroclinical RSE duration as a predictor.

Predicting myofiber cross-sectional area and triglyceride content with electrical impedance myography: A study in db/db mice.

BACKGROUND: Electrical impedance myography (EIM) provides insight into muscle composition and structure. We sought to evaluate its use in a mouse obesity model characterized by myofiber atrophy. METHODS: We applied a prediction algorithm, ie, the least absolute shrinkage and selection operator (LASSO), to surface, needle array, and ex vivo EIM data from db/db and wild-type mice and assessed myofiber cross-sectional area (CSA) histologically and triglyceride (TG) content biochemically. RESULTS: EIM data from all three modalities provided acceptable predictions of myofiber CSA with average root mean square error (RMSE) of 15% in CSA (ie, ±209 µm2 for a mean CSA of 1439 µm2 ) and TG content with RMSE of 30% in TG content (ie, ±7.3 nmol TG/mg muscle for a mean TG content of 25.4 nmol TG/mg muscle). CONCLUSIONS: EIM combined with a predictive algorithm provides reasonable estimates of myofiber CSA and TG content without the need for biopsy.

Estimating myofiber cross-sectional area and connective tissue deposition with electrical impedance myography: A study in D2-mdx mice.

INTRODUCTION: Surface electrical impedance myography (sEIM) has the potential for providing information on muscle composition and structure noninvasively. We sought to evaluate its use to predict myofiber size and connective tissue deposition in the D2-mdx model of Duchenne muscular dystrophy (DMD). METHODS: We applied a prediction algorithm, the least absolute shrinkage and selection operator, to select specific EIM measurements obtained with surface and ex vivo EIM data from D2-mdx and wild-type (WT) mice (analyzed together or separately). We assessed myofiber cross-sectional area histologically and hydroxyproline (HP), a surrogate measure for connective tissue content, biochemically. RESULTS: Using WT and D2-mdx impedance values together in the algorithm, sEIM gave average root-mean-square errors (RMSEs) of 26.6% for CSA and 45.8% for HP, which translate into mean errors of ±363 µm2 for a mean CSA of 1365 µm2 and of ±1.44 µg HP/mg muscle for a mean HP content of 3.15 µg HP/mg muscle. Stronger predictions were obtained by analyzing sEIM data from D2-mdx animals alone (RMSEs of 15.3% for CSA and 34.1% for HP content). Predictions made using ex vivo EIM data from D2-mdx animals alone were nearly equivalent to those obtained with sEIM data (RMSE of 16.59% for CSA), and slightly more accurate for HP (RMSE of 26.7%). DISCUSSION: Surface EIM combined with a predictive algorithm can provide estimates of muscle pathology comparable to values obtained using ex vivo EIM, and can be used as a surrogate measure of disease severity and progression and response to therapy.

The Connectivity Fingerprint of the Fusiform Gyrus Captures the Risk of Developing Autism in Infants with Tuberous Sclerosis Complex.

Tuberous sclerosis complex (TSC) is a rare genetic disorder characterized by benign tumors throughout the body; it is generally diagnosed early in life and has a high prevalence of autism spectrum disorder (ASD), making it uniquely valuable in studying the early development of autism, before neuropsychiatric symptoms become apparent. One well-documented deficit in ASD is an impairment in face processing. In this work, we assessed whether anatomical connectivity patterns of the fusiform gyrus, a central structure in face processing, capture the risk of developing autism early in life. We longitudinally imaged TSC patients at 1, 2, and 3 years of age with diffusion compartment imaging. We evaluated whether the anatomical connectivity fingerprint of the fusiform gyrus was associated with the risk of developing autism measured by the Autism Observation Scale for Infants (AOSI). Our findings suggest that the fusiform gyrus connectivity captures the risk of developing autism as early as 1 year of age and provides evidence that abnormal fusiform gyrus connectivity increases with age. Moreover, the identified connections that best capture the risk of developing autism involved the fusiform gyrus and limbic and paralimbic regions that were consistent with the ASD phenotype, involving an increased number of left-lateralized structures with increasing age.

Deletion of Neuronal GLT-1 in Mice Reveals Its Role in Synaptic Glutamate Homeostasis and Mitochondrial Function.

The glutamate transporter GLT-1 is highly expressed in astrocytes but also in neurons, primarily in axon terminals. We generated a conditional neuronal GLT-1 KO using synapsin 1-Cre (synGLT-1 KO) to elucidate the metabolic functions of GLT-1 expressed in neurons, here focusing on the cerebral cortex. Both synaptosomal uptake studies and electron microscopic immunocytochemistry demonstrated knockdown of GLT-1 in the cerebral cortex in the synGLT-1 KO mice. Aspartate content was significantly reduced in cerebral cortical extracts as well as synaptosomes from cerebral cortex of synGLT-1 KO compared with control littermates. 13C-Labeling of tricarboxylic acid cycle intermediates originating from metabolism of [U-13C]-glutamate was significantly reduced in synGLT-1 KO synaptosomes. The decreased aspartate content was due to diminished entry of glutamate into the tricarboxylic acid cycle. Pyruvate recycling, a pathway necessary for full glutamate oxidation, was also decreased. ATP production was significantly increased, despite unaltered oxygen consumption, in isolated mitochondria from the synGLT-1 KO. The density of mitochondria in axon terminals and perisynaptic astrocytes was increased in the synGLT-1 KO. Intramitochondrial cristae density of synGLT-1 KO mice was increased, suggesting increased mitochondrial efficiency, perhaps in compensation for reduced access to glutamate. SynGLT-1 KO synaptosomes exhibited an elevated oxygen consumption rate when stimulated with veratridine, despite a lower baseline oxygen consumption rate in the presence of glucose. GLT-1 expressed in neurons appears to be required to provide glutamate to synaptic mitochondria and is linked to neuronal energy metabolism and mitochondrial function.SIGNIFICANCE STATEMENT All synaptic transmitters need to be cleared from the extracellular space after release, and transporters are used to clear glutamate released from excitatory synapses. GLT-1 is the major glutamate transporter, and most GLT-1 is expressed in astrocytes. Only 5%-10% is expressed in neurons, primarily in axon terminals. The function of GLT-1 in axon terminals remains unknown. Here, we used a conditional KO approach to investigate the significance of the expression of GLT-1 in neurons. We found multiple abnormalities of mitochondrial function, suggesting impairment of glutamate utilization by synaptic mitochondria in the neuronal GLT-1 KO. These data suggest that GLT-1 expressed in axon terminals may be important in maintaining energy metabolism and biosynthetic activities mediated by presynaptic mitochondria.

A Stroke Alert Protocol Decreases the Time to Diagnosis of Brain Attack Symptoms in a Pediatric Emergency Department.

OBJECTIVE: To determine whether a stroke alert system decreases the time to diagnosis of children presenting to the emergency department (ED) with acute-onset focal neurologic deficits. STUDY DESIGN: We performed a retrospective comparison of clinical and demographic information for patients who presented to the ED of a tertiary children's hospital with acute-onset focal neurologic deficits during the 2.5 years before (n = 14) and after (n = 65) the implementation of a stroke alert system. The primary outcome was the median time to neuroimaging analyzed using a Wilcoxon rank-sum test. RESULTS: The median time from ED arrival to neuroimaging for patients with acute-onset focal neurologic deficits decreased significantly after implementation of a stroke alert system (196 minutes; IQR, 85-230 minutes before [n = 14] vs 82 minutes; IQR, 54-123 minutes after [n = 65]; P < .01). Potential intravenous tissue plasminogen activator candidates experienced the shortest time to neuroimaging after implementation of a stroke alert system (54 minutes; IQR, 34-66 minutes [n = 13] for intravenous tissue plasminogen activator candidates vs 89.5 minutes; IQR, 62-126.5 minutes [n = 52] for non-intravenous tissue plasminogen activator candidates; P < .01). CONCLUSIONS: A stroke alert system decreases the median time to diagnosis by neuroimaging of children presenting to the ED with acute-onset focal neurologic deficits by more than one-half. Such a protocol constitutes an important step in ensuring that a greater proportion of children with arterial ischemic stroke are diagnosed in a time frame that enables hyperacute treatment.

Photoplethysmographic evaluation of generalized tonic-clonic seizures.

OBJECTIVE: Photoplethysmography (PPG) is an optical technique measuring variations of blood perfusion in peripheral tissues. We evaluated alterations in PPG signals in relationship to the occurrence of generalized tonic-clonic seizures (GTCSs) in patients with epilepsy to evaluate the feasibility of seizure detection. METHODS: During electroencephalographic (EEG) long-term monitoring, patients wore portable wristband sensor(s) on their wrists or ankles recording PPG signals. We analyzed PPG signals during three time periods, which were defined with respect to seizures detected on EEG: (1) baseline (>30 minutes prior to seizure), (2) preseizure period, and (3) postseizure period. Furthermore, we selected five random control segments during seizure-free periods. PPG features, including frequency, amplitude, duration, slope, smoothness, and area under the curve, were automatically calculated. We used a linear mixed-effect model to evaluate changes in PPG features between different time periods in an attempt to identify signal changes that detect seizures. RESULTS: We prospectively enrolled 174 patients from the epilepsy monitoring unit at Boston Children's Hospital. Twenty-five GTCSs were recorded from 13 patients. Data from the first recorded GTCS of each patient were included in the analysis. We observed an increase in PPG frequency during pre- and postseizure periods that was higher than the changes during seizure-free periods (frequency increase: preseizure = 0.22 Hz, postseizure = 0.58 Hz vs changes during seizure-free period = 0.05 Hz). The PPG slope decreased significantly by 56.71 nW/s during preseizure periods compared to seizure-free periods. Additionally, the smoothness increased significantly by 0.22 nW/s during the postseizure period compared to seizure-free periods. SIGNIFICANCE: Monitoring of PPG signals may assist in the detection of GTCSs in patients with epilepsy. PPG may serve as a promising biomarker for future seizure detection systems and may contribute to future seizure prediction systems.

Photoplethysmography: A measure for the function of the autonomic nervous system in focal impaired awareness seizures.

OBJECTIVES: Photoplethysmography (PPG) reflects variations of blood perfusion in tissues, which may signify seizure-related autonomic changes. The aim of this study is to assess the variability of PPG signals and their value in detecting peri-ictal changes in patients with focal impaired awareness seizures (FIASs). METHODS: PPG data were recorded using a wearable sensor placed on the wrist or ankle of children with epilepsy admitted for long-term video-electroencephalographic monitoring. We analyzed PPG data in four different periods: seizure-free, preictal, ictal, and postictal. Multiple features were automatically extracted from the PPG signal-frequency, duration, amplitude, increasing and decreasing slopes, smoothness, and area under the curve (AUC)-and were used to identify preictal, ictal, or postictal changes by comparing them with seizure-free periods and with each other using a linear mixed-effects model. RESULTS: We studied PPG in 11 patients (18 FIASs), including seizure-free, preictal, and postictal periods, and a subset of eight patients (12 FIASs) including the ictal period. Compared to the seizure-free period, we found significant changes in PPG (1) during the ictal period across all features; (2) during the preictal period in amplitude, duration, increasing slope, and AUC; and (3) during the postictal period in decreasing slope. SIGNIFICANCE: Specific PPG changes can be seen before, during, and after FIASs. The peri-ictal changes in the PPG features of patients with FIASs suggest potential applications of PPG monitoring for seizure detection.